From owner-freebsd-questions@freebsd.org Mon Apr 18 22:26:38 2016 Return-Path: Delivered-To: freebsd-questions@mailman.ysv.freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2001:1900:2254:206a::19:1]) by mailman.ysv.freebsd.org (Postfix) with ESMTP id 29B26B13A5D for ; Mon, 18 Apr 2016 22:26:38 +0000 (UTC) (envelope-from shamim.shahriar@gmail.com) Received: from mail-wm0-x231.google.com (mail-wm0-x231.google.com [IPv6:2a00:1450:400c:c09::231]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (Client CN "smtp.gmail.com", Issuer "Google Internet Authority G2" (verified OK)) by mx1.freebsd.org (Postfix) with ESMTPS id A9F041B52 for ; Mon, 18 Apr 2016 22:26:37 +0000 (UTC) (envelope-from shamim.shahriar@gmail.com) Received: by mail-wm0-x231.google.com with SMTP id 127so1151448wmz.0 for ; Mon, 18 Apr 2016 15:26:37 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20120113; h=subject:to:references:cc:from:message-id:date:user-agent :mime-version:in-reply-to; bh=aKvoZPMWa5P/q4fNH8HrYntvzzY3Q6+AAVZEos1Zrq4=; b=HTsDWHxlHVmE7D4WEfiT3LvgqOk5gDZsluN58Xts/DIWuxl6vLPhng+/qaKV6iqfFt EMAwaw2Xm2ukGvkG4/xqiVE8Rx9cXUjqpAOO6PTpabUjSYG5I9A8wkTkCdAajPX8Rlfe Y3qgRg4IXXL7BCSOBFjo6Mu/cCgLALVp6oruk9MbcnQ64jSsFD5JLzS4icwt7+XsEWYC W0kzseRRBHmIiL13M4d/7N2q2EYUg7pQ3EflUcykdIafeW6uO1ygzGVgkwqMhxcSx4K+ lFFRwk5V3NP4VSpFeFdVW1oQURwJGvQUAYGfzwZEDPkiasiGQ7METX31q+PgHljc9WxY fNEQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20130820; h=x-gm-message-state:subject:to:references:cc:from:message-id:date :user-agent:mime-version:in-reply-to; bh=aKvoZPMWa5P/q4fNH8HrYntvzzY3Q6+AAVZEos1Zrq4=; b=OVQNO4mslYm0ih2sKMiF9yNq6PWOGhhjUEw2728udXmW2Xn2Cc4wI4wjf1stebjNkj ynS+Jj04JwXAqN8qjZN1FCXwk5AbvhUtSSwjZoAjhXKstKm4oszd7O1gmNv8nAm2GoRy eOkEwE9QdOPkWauZIkfXm5VAFJ2gjWoABAQt9EFG+B4b7+Eo6s/wHNW+oxM6hkCSjIIC bBeDiXw7IgXbm4WQtuBgj5jtUH5y/gRwraF07fMap4mVBz0/xioQqAbFw/8ihk88tUts XNsMnKaL0HrSasR7qThhI4cHwKOHsArbNVEJfHLUZvjwKRVbRHvI8xVOwn9pPvNjM7KT ZBPA== X-Gm-Message-State: AOPr4FWt+bVBp2Oz1B8HKhcNaLyCim9o5Hqc4YaHsZ5GNFrHM1wCkq/G4etPgfKgnU8CBg== X-Received: by 10.28.144.8 with SMTP id s8mr20111373wmd.39.1461018395382; Mon, 18 Apr 2016 15:26:35 -0700 (PDT) Received: from osk.homenet ([2001:470:196e:13:f2de:f1ff:fed1:783c]) by smtp.googlemail.com with ESMTPSA id kq9sm66276064wjc.26.2016.04.18.15.26.34 (version=TLSv1/SSLv3 cipher=OTHER); Mon, 18 Apr 2016 15:26:34 -0700 (PDT) Subject: Re: Raid 1+0 To: "Brandon J. Wandersee" , "Kevin P. Neal" References: <571533F4.8040406@bananmonarki.se> <57153E6B.6090200@gmail.com> <20160418210257.GB86917@neutralgood.org> <86k2jupo7b.fsf@WorkBox.Home> Cc: freebsd-questions@freebsd.org From: Shamim Shahriar X-Enigmail-Draft-Status: N1110 Message-ID: <57155F19.6090203@gmail.com> Date: Mon, 18 Apr 2016 23:26:33 +0100 User-Agent: Mozilla/5.0 (X11; FreeBSD amd64; rv:38.0) Gecko/20100101 Thunderbird/38.4.0 MIME-Version: 1.0 In-Reply-To: <86k2jupo7b.fsf@WorkBox.Home> Content-Type: text/plain; charset=windows-1252 Content-Transfer-Encoding: 7bit X-Content-Filtered-By: Mailman/MimeDel 2.1.21 X-BeenThere: freebsd-questions@freebsd.org X-Mailman-Version: 2.1.21 Precedence: list List-Id: User questions List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Mon, 18 Apr 2016 22:26:38 -0000 On 18/04/2016 23:05, Brandon J. Wandersee wrote: > Kevin P. Neal writes: > >> On Mon, Apr 18, 2016 at 09:07:07PM +0100, Shamim Shahriar wrote: >>> On 18/04/2016 20:22, Bernt Hansson wrote: >>>> Hello list >>>> >>>> >>>> Used gstripe to stripe the arrays raid/r0 + r1 into stripe0 >>>> >>> Hi >>> >>> I'm sure there are people with more expertise than I am, and they can >>> confirm either ways. But in my mind, given that you used RAID1 first >>> (mirror) and then used those two RAID1 to create a RAID0, this is >>> logically RAID 1+0. In other words, if you lose one disc from each of >>> the RAID1 you are still safe. If you lose both from one single mirror >>> array (highly unlikely), the stripe is unlikely to be of any use. >> Not that unlikely. If you take identical disks from the same company and >> subject them to identical load then the probability that they will fail >> around the same time is much higher than random. >> >> That's why when I set up a mirror I always build it with drives from >> different companies. And I make it a three way mirror if I can. > Sorry to drag this off-topic, but I've heard this advice more than once > now, and have to ask: when you say "same company," do you mean same > vendor or same manufacturer? I thought having all disks be of the same > make and model was ideal, as it avoids problems arising from the different > ways each manufacturer fudges their total disk capacity. If I'm wrong, > how so? If you mean buying disks of the same make and model from > different vendors is ideal, what's the reasoning there? > > Oh No! now you have initiated what we call a "holy war" :P :P :P There are schools that advocate on either sides. Personally, I am yet to encounter any issues arising from drives from the same vendor same batch same shipment -- and that is over the last thirty odd years. I generally tend to change the drives from the array every 3 years (if not earlier), keep additional backup (when it is practical) -- and have not had any issues. On the other hand, I'm sure plenty of people on this list had issues and have vowed never to use identical drives on their array. As for drive failure probability -- as the probability theory says -- the chance might be infinitesimally small, but never zero. So yes, you /might/ loose a disc due to solar radiation, higher temperature on the server cabinet, misconfiguration on your array (different sized drive can sometimes be confusing, you accommodate for the lowest size, but the bigger one has no way of automagically distribute data for the areas it is not using) -- and so many unpredictable/unforeseen/unaccounted for reasons. But those situations aside, as stated, I have lost drives for various other reasons, but not from a raid array and definitely not because they were from the same batch/make/model. And again, with all due respect, I know there are people who did lose drive and eventually the data, and have vowed never to use drives from same vendor/supplier in the same array, and I respect that. Just stating I never had that issue. Hope this helps.